File chooser dialog ignores drive Z

[squash]

fyne/dialog/file_windows.go

Line 37 in 0ca05dc

for i := 0; i < 24; i++ {

Unless I'm reading this wrong, it's only looking at the first 25 letters and ignoring Z:, which is the default for a mapped network drive.

[andydotxyz]

I think it's probably a typo that should read 26 - it is missing Y and Z if I read it correctly

[andydotxyz]

Fixed on release/v1.4.x branch, will release in v1.4.1.